This invention relates to polymers useful as multipurpose additives for lubricating oils and hydrocarbon motor fuels. More particularly, this invention concerns diene-modified mono-olefinic backbone polymers functionalized with chlorosulfonyl isocyanate and post-reacted with a nitrogen compound. The polymers combine viscosity index improvement with detergent properties when used in lubricating oils and hydrocarbon motor fuels.
The continuing search for multi-purpose lubricating oil and hydrocarbon motor fuel additives has led recently to families of graft copolymers. Representative of these additives are polyolefinic viscosity index improving backbone polymers grafted with polar monomers such as methyl methacrylate, N,N-diethylaminoethyl methacrylate, C-vinylpyridine and N-vinylpyrrolidone, as in U.S. Pat. Nos. 3,404,091, 3,687,849 and 4,146,489. Other developments have proceeded along the lines of incorporating the polar functionality needed for detergency by grafting monomers such as maleic anhydride onto a polyolefinic backbone polymer and then post-reacting the carboxylic functionality of the maleic anhydride with polar compounds containing nitrogen and/or oxygen, such as amines and alkane polyols, as in U.S. Pat. Nos. 3,914,203, 4,033,888, 4,033,889, 4,036,772, 4,089,794 and 4,169,063.
The development of such polymeric additives, however, has not been without difficulty, due in part to the presence or the formation of haze in concentrates of the polymeric additives. The haze normally does not detract from the end use properties of the additives but it is undesirable from the standpoint of consumer acceptance and general marketability. Attempts to cure this problem have led to improvements involving nitrogen containing monomer or maleic anhydride grafting such as described in U.S. Pat. Nos. 4,069,162, 4,160,739, 4,161,452 and 4,144,181. Nevertheless, monomer grafting techniques continue to involve problems of control, in terms of homopolymer by-product formation, haze due to gelation and other causes, dispersancy levels (in terms of yield of active product or percent product derivitized), and balance of properties.
Other attempts to produce multipurpose additives for lubricating oils and hydrocarbon motor fuels have involved incorporating the polar functionality required for detergency by including polar monomers with the monomers used to form the substrate polymer, or by treating a polymeric substrate with oxidizing agents or other reactants for direct derivatization of the polymer. U.S. Pat. No. 3,328,297 to Anderson discloses the incorporation of polyamino functionality into polyolefinic substrate polymers by functionalizing the substrate polymer with chlorosulfonyl isocyanate and then post-reacting with an alkylene polyamine or polyalkylene polyamine. However, the products obtained have been found lacking in viscosity index (VI) improving properties. Moreover, when in the course of the work leading to the present invention it was attempted to incorporate the VI improving properties by substituting a higher molecular weight version of the polyolefin as the substrate polymer in the examples of the patent, the percent of product derivitized was lower than expected and certain of the products, such as those prepared from polyisobutylene-isoprene substrate polymer were oil-insoluble and therefore useless as lubricating oil or motor fuel additives.
The present invention therefore has as an object the provision of multi-purpose additives for lubricating oils and hydrocarbon motor fuels based upon the derivitization of polymeric viscosity index improving materials, by functionalization with chlorosulfonyl isocyanate followed by reaction with a nitrogen compound thus providing high yield (approaching 100% active material) of active product but without substantial gel formation and production of the haze which often accompanies graft polymerizations.